#include<iostream>
#include<vector>
using namespace std;
//int dp[N];
int main()
{
	int n;
	cin >> n;
	if (n == 1 || n == 2)return n;
	if (n == 3)return 4;
	const int mod=1e9+7;
	vector<int>dp(n+1);
	dp[1] = 1, dp[2] = 2, dp[3] = 4;
	for (int i = 4; i <= n; i++)
	{
		dp[i] = ((dp[i - 1] + dp[i - 2]) % mod + dp[i - 3]) % mod;
	}
	cout << dp[n] << endl;
}
